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How to get numbers from rows in a matrix, to separate vectors?

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Emil Christensen
Emil Christensen on 23 Jan 2020
Edited: Stephen Cobeldick on 27 Jan 2020
I have a matrix of grades, I want to put the number of times grades repeat in each row into separate vectors so I can plot it in a scatter plot.
I have the matrix
grades=
7 7 4
12 10 10
-3 7 2
10 12 12
4 2 10
10 7 4
7 7 9
12 12 12
2 7 12
0 -3 2
4 10 2
2 12 10
10 3 4
12 12 12
I want to know how many times each number repeats in each row, and put them in a vector for each row

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Answers (1)

Samatha Aleti
Samatha Aleti on 27 Jan 2020
According to my understanding you are trying to get the count of numbers in each row and save it in another vector. You can use “find” function to do this.
Let grades be the matrix, out be the output vector which holds the count of element “1” in each row.Here is a sample code to do this:
grades = [1 2 3; 3 2 1; 1 2 1; 1 2 3; 1 3 1;1 1 3]; % Let
numRows = size(grades,1); % Number of rows
out= zeros(1,numRows); % Initialize a vector to store the count
for i = 1:numRows
out(i) = length(find(grades(i,:) == 1));
end
Refer the following document link for detailed explanation on using "find":

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Stephen Cobeldick
Stephen Cobeldick on 27 Jan 2020
More efficient than using length(find(...)):
nnz(grades(i,:) == 1)

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